Electron discharge device



March 26, 1968 c; E. MAIER 3,375,395 I ELECTRON-DISCHARGE DEVICE Filed A ril 12. 1965 .IYNVENETOR: CLETUS s. MAIER,

- H s ATTORNEY United States Patent 3,375,395 ELECTRON DISCHARGE DEVICE Cletus E. Maier, Cannelton, Ind., assiguor to General Electric Company, a corporation of New York Filed Apr. 12, 1965, Ser. No. 447,422 Claims. (CL. 313318) ABSTRACT OF THE DISCLOSURE This invention proposes an electric discharge device which comprises an envelope, a cathode assembly supported in one end of the envelope, and an anode assembly supported in the other end of the envelope. The anode assembly includes a tubular top cap of; relatively thin conductive material which extends through and is sealed in one end wall of the envelope. The top cap has an external contact portion with a distortion blocking circumferential groove located adjacent the envelope Wall. Preferably thegroove is of semicircular cross-sectional shape, with a depth to material thickness ratio of approximately 2 to 1 and a width to depth ratio of approximately 3 to l.-

This invention relates to an electron discharge device and more particularly to an improved terminal connection therefor.

In certain electron discharge devices, such as high voltage rectifiers, it is necessary to maintain the anode connection completely isolated from the cathode leads because of the high potential difference therebetween and an anode terminal connection is, therefore, provided at the top of the envelope of the device called a top cap. In the high dissipation type of tube this top cap is the form of a tubular member which extends into the envelope for the device and is sealed with a portion of the envelope wall providing an internal portion thereof which may be directly connected to the anode and an external portionwhich extends outwardly from the envelope wall to permit external electric connection to be made thereto. A major difliculty encountered with this type of construction lies in the fact that when a connector, which usually has spring fingers, is-inserted' over the external top cap portion, distorti'on of the side walls of the top'cap by the spring fingers'causesa rupture of the glass-metal seal between the top-cap and the glass wall of the envelope causing a gas leak into the envelope of the device and ultimate destruction thereof.

The primary object of the invention is to provide a new and improved top cap terminal'connection for an electron discharge device which overcomes the abovementioned defect.

A further object of the invention is to provide a new and improved high voltage rectifier having an improved top cap which is less susceptible to destruction of the seal as a result of distortion of the top cap,

It is a further object of this invention to provide a new and improved anode assembly for a high voltage rectifier equipped with means for preventing distortion of the seal portion thereofas a result of pressure applied to the terminal connection portion thereof.

, Further objects and advantages of the invention will become apparent as the following description proceeds Patented Mar. 26, 1968 and the features and novelty which characterize the mvention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

In carrying out the objects of the invention there is provided an electric discharge device which comprises an envelope, a cathode assembly supported in one end of the envelope and an anode assembly supported in the other end of the envelope. The anode assembly includes a tubular top cap of relatively thin conductive material which extends through and is sealed in one end wall of the envelope. This top cap has an external contact portion with a distortion blocking circumferential groove located adjacent the envelope wall. Preferably the groove is of a semi-circular cross sectional shape, with a depth to material thickness ratio of approximately 2 to 1 and a width to depth ratio of approximately 3 to 1.

For a better understanding of the invention reference may be had to the accompanying drawing in which:

I FIGURE 1 is an elevational view of an electric discharge device incorporating the invention and partially broken away to show the interior thereof, and

7 FIGURE 2 is an enlarged sectional view With certain parts broken away, better illustrating the form of the improved top cap constructed in accordance with the invention.

Referring to FIGURE 1 there is shown an electric dis charge device in the form of a highvoltage rectifier tube generally designated 3. The tube includes a glass bulb or envelope 5 in which is housed an anode assembly 7 mounted in a suspended manner in the envelope by means of a top cap 9 which extends through and is suitably vacuum-sealed in the top wall portion of the envelope 5. The anode assembly 7 further includes a cylindrical anode 1.1 which may be of any form, one of the common forms being the bell-shaped form shown in the drawing. Further details of a suitable anode construction are more fully disclosed in US. Patent No. 3,080,498; Hammond et a1. assigned to the assignee of this application.

Mounted in the envelope by a pair of vetrical support rods 13 and disposed in the anode 11 is the filament or cathode 15. Suitably supported beneath the anode and in spaced relation thereto is a shield 17. The lower end of the envelope forms a base 19 carrying a plurality of base pins 21, Leads 25 are electrically connected to the various pins 21 and extend in a sealed manner through the lower end of the envelope for making electrical connections to and supporting the filament support rods 13 and shield 17 in the envelope.

The top cap 9, best shown in FIGURE 2 is a thin-walled hollow tubular structure which includes an internal portion 27 contained within the envelope 5 and connected to anode 11 by a suitable flange 29, an external portion 31 and an intermediate seal portion 33. A hermetic seal 35 is formed between the top wall of the envelope 5 and intermediate seal portion 33 of the top cap 9. The external portion 31 of the top cap 9 is closed at its outer end by end wall 37 and a distortion blocking groove 39 is provided therein adjacent seal portion 33.

' As diagrammatically shown in FIGURE 2, a highvoltage electrical connector 41 which 'is commonly of porcelain or other suitable insulative material is placed over the top cap 9 to make electrical connection to the anode 11 when the tube is to be operated. This connector 41 includes at least one spring finger 43 which is suitably connected to a flexible or other conductor (not shown), the Spring finger being biased into good electrical connection with the top cap 9. The pressure exerted thereon by the spring finger can cause distortion of the top cap 9 since the latter is made of relatively thin material and the spring tension is relatively high for good contact. This distortion in many cases can be sufficient to break the seal 35 between the seal portion 33 of the top cap and the envelope 5 unless, in accordance with the invention, there is provided between the external connection portion 31 of the top cap and the seal portion 33, the distortion blocking means 39. While the exact mechanism by which the groove blocks distortion and substantially eliminates rupture of the seal 35 is not known, it is believed that the groove directs the distortion stresses at right angles to the longitudinal length of the tubular top cap 9 instead of permitting them to act along its axial length as would be the case when the distortion blocking groove is not present. Therefore, the distortion does not reach the seal portion, or, the amount of distorting force reaching the sealed portion with applicants improved top cap is insufficient to disrupt the seal between the walls of the envelope and the seal portion of the top cap.

Qu-antitatively, top caps of the type conventionally used have had the ability to withstand pressures in the range of from 40 to 50 lbs., depending on the point on the top cap of application of the pressure. When maximum pressure has been applied closely adjacent, say, from 1 to 2 millimeters from the seal portion of the top cap, the seal has been ruptured by pressures of less than 40 lbs. Top caps made in accordance with the invention having a distortion blocking groove have been found to withstand pressures in the range of from 80 to 90 lbs. and while under most favorable conditions, when conventional caps failed at approximately 50 lbs. pressure, the top caps of my invention have withstood pressures of over 150 lbs. without rupturing the glass-metal seals.

In the preferred embodiment of the invention the top cap is made from material having a thickness of 0.012 inch with the groove being of a semicircular cross section and having a depth of 0.020 inch and a width of 0.060 inch. When the width of the groove is increased to 0.120 inch, an improvement over conventional top caps is observed, but the improvement is not as great as demonstrated by the preferred embodiment. Therefore, it is preferred that the width to depth ratio of the groove should be in the range of at least 2:1, and less than 6:1, and that the depth to material thickness ratio should be ap proximately 2:1. In the preferred embodiment, it will be noted that the width-depth ratio is approximately 3:1.

While specific forms of the invention have been shown and described, it is not desired that the invention is to be limited to the particular forms shown and described, but that the modifications which fall within the spirit and scope of our invention are intended to be covered by the appended claims.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A top cap for an electron discharge device comprising an elongated tubular member of relatively thin conductive material, said member having opposed electrical connection portions, an intermediate seal portion, and means for blocking distortion of said seal portion resulting from pressure applied to one of said electrical connection portions, said means being located substantially entirely between one of said connection portions and said seal portion. V I

2. A top cap for an electron discharge. device comprising a tubular member of relatively thin conductive material, said member having an internal electrical connection portion, an intermediate seal portion, and an external electrical connection portion; and means for blockingdistortion of said seal portion resulting from pressure applied to said external portion, said means comprising a circumferential groove located between said external portion and said seal portion.

3. A top cap for an electron discharge device comprising a tubular member of relatively thin conductive material, said member having an internal electrical connec tion portion, an intermediate seal portion, and an external electrical connection portion; and means for blocking distortion of said seal portion resulting from pressure applied to said external portion, said means comprising a circumferential groove of semicircular cross section located between said external portion and said seal portion.

4. An electrode assembly for an electron discharge device comprising an electrode and a top cap of relatively thin conductive material secured together, said top cap having an internal electrical connection portion, secured to the electrode; an intermediate seal portion, and an external electrical connection portion; and means for blocking distortion of said seal portion resulting from pressure applied to said external portion, said means being located between said external portion and saidv seal portion.

5. An electrode assembly for an electron discharge device comprising an electrode and a top cap of relatively thin conductive material, said member having an internal electrical connection portion secured to the electrode; an intermediate seal portion, and an external electrical connection portion; said portion being adapted for receiving a contact member exerting pressure over a limited surface thereof and substantially hollow groove means for blocking distortion of said seal portion resulting from pressure applied to said limited surface, said means located between said limited surface and said seal portion.

6. An electron discharge device comprising an envelope; a cathode assembly supported in one end of said envelope; and an anode assembly supported in the other end of said tube and including a tubular top cap extending through and sealed in the one end wall of said envelope, said top cap including an external contact portion having a distortion blocking circumferential groove therein located substantially entirely between said external contact portion and said envelope wall.

7. An electron discharge device comprising an envelope; a cathode assembly supported in one end of said envelope; and an anode assembly supported in the other end of said tube and including a tubular top cap of relatively thin conductive material extending through and sealed in the one end wall of said envelope, said top cap including an external contact portion having a hollow distortion blocking circumferential groove located adjacent the envelope wall.

8. An electron discharge device comprising an envelope; a cathode assembly supported in one end of said envelope; and an anode assembly supported in the other end of said tube and including a tubular top cap extending through and sealed in the one end wall of said envelope, said top cap including an external contact portion having a distortion blocking circumferential groove therein located adjacent the envelope wall, said groove being hollow and having a generally semicircular cross-sectional shape.

9. An electron discharge device comprising an envelope; a cathode assembly supported in one end of said envelope; and an anode assembly supported in the other end of said tube and including a tubular top cap of relatively thin conductive material extending through and sealed in the one end wall of said envelope, said top cap including an external contact portion having a distortion blocking circumferential groove therein located adjacent the envelope wall, said groove having a width to depth ratio of at least 2:1 and less than 6:1.

10. A high-voltage rectifier tube comprising an envelope; a cathode assembly supported in one end of said envelope, an anode assembly supported in the other end of said tube and including a tubular top cap of relatively thin conductive material extending through and sealed in the one end wall of said envelope, said top cap includ- 2,888,590 5/1959 Taylor 313299 ing an external contact portion having a distortion block- ,9 1960 l an 6t 31. 313331 ing circumferential groove located adjacent the envelope FOREIGN PATENTS Wall, said groove having a generally semicircular crosssectional shape with a depth to material thickness ratio 5 9'27943 5/1955 Germany of approximately 2:1. OTHER REFERENCES RCA Technical Notes, No. 63, Strain Isolating Vacuum References cued Tube Terminal, by Curtis et al. UNITED STATES PATENTS 10 JOHN W. HUCKERT, Primary Examiner.

2,250,647 7/1941 Miller 313318 A. 1. JAMES, Assistant Examiner. 

